Primary Liposarcoma

770 Hunt, Attanoos, Jasani

for immunohistochemical staining based on microwave 7 Norton AJ, Jordan S, Yeomans P. Brief, high-temperature oven heating of tissue sections. J Histochem Cytochem heat denaturation (pressure cooking): a simple and retrieval for routinely proc- 1991;39:741-8. effective method of antigen J Clin Pathol: first published as 10.1136/jcp.49.9.770 on 1 September 1996. Downloaded from 6 Navabi H, Douglas-Jones A, Bankfalvi A, Schmid K, Suzuki essed tissues. J Pathol 1994;173:371-9. K, Katoh R, et al. Wet autoclave pretreatment: a reliable 8 Morgan JM, Navabi H, Schmid K, Jasani B. Possible role of alternative to microwave technique for antigen retrieval tissue-bound calcium ions in citrate-mediated high- [abstract]. J Pathol 1994;172:50A. temperature antigen retrieval. J Pathol 1994;174:301-7.

JT Clin Pathol 1996;49:770-772 Focal rhabdomyosarcomatous differentiation in primary liposarcoma

J H Shanks, SS Banerjee, B P Eyden

Abstract Case report A unique case of primary myxoid liposar- A 75 year old man presented with a six week coma of the thigh, in which focal pleomor- history of a swelling in the right thigh. This was phic areas were present containing associated with oedema of the right leg, but rhabdomyoblasts, is described. Focal rhab- there were no systemic symptoms. There was domyosarcoma in liposarcoma has only no evidence of any abdominal mass. On explo- rarely been reported previously and only ration, a mass was found to be displacing, but in dedifferentiated liposarcomas of the not invading, the femoral vessels and nerves. retroperitoneum. All but one have been The tumour was easily mobilised except on the recurrences with rhabdomyoblasts being posterior surface where it was adherent to the absent in the primary liposarcoma. As pectineus muscle. rhabdomyoblasts were only focally Macroscopically, the tumour consisted of a present, the present case is regarded as partly encapsulated fatty mass measuring 12 liposarcoma with focal divergent rhab- cm at its maximum dimension with a small domyoblastic differentiation rather than amount ofsurrounding soft tissue. It was partly malignant mesenchymoma. necrotic. Histologically, the tumour was a (7 Clin Pathol 1996;49:770-772) liposarcoma which was predominantly of

myxoid type with a typical delicate branching http://jcp.bmj.com/ Keywords: liposarcoma, rhabdomyosarcoma, malignant capillary network and myxoid stroma (fig 1). In mesenchymoma. places, the tumour had more cellular pleomorphic areas. The latter were composed of Liposarcoma may contain benign or malignant spindle cells with notable nuclear pleomor- heterologous mesenchymal elements. Benign phism and bizarre lipoblasts containing typical cartilage,' smooth muscle,2 or rarely bone' have scalloped nuclei and cytoplasmic lipid vacuoles

been described in well differentiated lipo- (fig 1, left upper inset). Mitotic activity was fre- on September 24, 2021 by guest. Protected copyright. sarcoma/atypical lipomatous tumours or in quent (21/10 high power fields) within the myxoid liposarcoma. Until now, malignant pleomorphic areas and large foci of necrosis heterologous elements have been found only in were seen. The tumour grade was 3 based on dedifferentiated liposarcoma.' " the method by Trojani et al.6 Malignant myogenic elements found in Cells within the pleomorphic areas had liposarcoma have included leiomyosarcoma, abundant eosinophilic cytoplasm and notice- rhabdomyosarcoma, or both. Other heterolo- ably hyperchromatic nuclei (fig 1, right lower gous elements including angiosarcoma or oste- inset), many showing notable nuclear enlarge- oid have also been described rarely.' Divergent ment and irregular nuclear contours. Pleomor- rhabdomyosarcomatous differentiation has phic multinucleate tumour giant cells were also been reported previously in only seven cases of seen. No cross striations were visible by light liposarcoma.' 3-5 All were dedifferentiated li- microscopy. Immunohistochemistry was per- posarcomas arising in the retroperitoneum and formed using the streptavidin-peroxidase com- in all but one case rhabdomyosarcoma was plex technique with diaminobenzidine chro- found only in tumour recurrences. There is mogen substrate. The pleomorphic cells only a single previous case of rhabdomyosarco- showed intense cytoplasmic positivity using Department of matous differentiation in de novo liposarcoma, immunostains for desmin (diluted 1 in 25; Histopathology, Christie Hospital NHS a retroperitoneal dedifferentiated tumour.5 Dako, High Wycombe, UK). Myoglobin (di- Trust, Wilmslow Road, Here, we describe a unique case of divergent luted 1 in 1000; Dako) and muscle specific Withington, rhabdomyosarcomatous differentiation in a de actin (HHF 35) (diluted 1 in 40; Biomen, Fin- Manchester M20 4BX novo liposarcoma, which was of combined champstead, UK) were also positive in these Correspondence to: myxoid and pleomorphic subtypes arising in cells. A proportion of them were positive for Dr SS Banerjee. the thigh. Immunohistochemical and ul- fast myosin (diluted 1 in 600; Sigma, Poole, 1 Accepted for publication trastructural evidence is provided to support Dorset, UK) and sarcomeric actin (diluted in 7 May 1996 our diagnosis. 100; Sigma). No tumour cells stained for Focal rhabdomyosarcomatous differentiation in primary liposarcoma 771

V.IF t, Discussion Until now the presence of heterologous rhab- FN~ Frx *s domyoblastic elements has been described J Clin Pathol: first published as 10.1136/jcp.49.9.770 on 1 September 1996. Downloaded from only in seven cases of liposarcoma.1 " In one of these cases divergent rhabdomyosarcoma and leiomyosarcoma were present concur- *,sR rently.' Malignant heterologous elements were found only in recurrent dedifferentiated retroperitoneal liposarcomas except for one previous case in which rhabdomyosarcoma was present in a de novo dedifferentiated retroperitoneal liposarcoma.5 - Our case is the first account of liposarcoma with divergent rhabdomyosarcomatous differ- ~'~"' entiation at a site other than the retroperitoneum. Our case is only the second reported r s example of rhabdomyosarcomatous differen- ;w*t tiation in the initial excision specimen of a /# liposarcoma rather than in a recurrence. i Furthermore, until now rhabdomyoblastic dif- Figure 1 Myxoid liposarcomatous area (L) merging with a rhabdomyosarcomato7us area ferentiation had not been described in either (R). Inset upper left: typical lipoblast; inset lower right: typical rhabdomyoblast (haemotoxylin and pleomorphic or in combined myxoid and pleo- eosin). morphic liposarcoma, having only been found in dedifferentiated liposarcoma. -i Dedifferentiated liposarcoma as originally described by Evans7 contains well differenti- <,,;ated liposarcoma in addition to a cellular mitotically active spindle cell component in which lipogenesis (presence of lipoblasts) is lacking. Our case contrasts with dedifferenti- .=4+* ated liposarcoma in two respects. Firstly, it was composed predominantly of myxoid liposarcoma rather than well differentiated liposar- 4 coma. Secondly, lipogenesis was clearly identi- fied in the pleomorphic areas of our tumour. ~ i This component therefore fulfilled the criteria for pleomorphic liposarcoma.7 A combination

= of myxoid and pleomorphic liposarcoma as http://jcp.bmj.com/ noted in our case is unusual although all com- =-+ bined types represent approximately 5 to 10% of cases of liposarcoma.8 None of the previous cases with divergent rhabdomyosarcomatous differentiation were of pure myxoid type, although Salanzo et al reported that some

myxoid areas were present concurrently. on September 24, 2021 by guest. Protected copyright.

Xsk It could be argued that our case is an example of malignant mesenchymoma, a term originally proposed in 1948 by Stout.9 Malignant mesenchymoma was defined as a sarcoma Figure 2 Electron micrograph showing sarcomeric myofibrils (arrow, A), Z-disks composed of two unrelated differentiated mes- (arrowheads, A) and an individual niyofibril with thick straight myosin filaments B). A, x13 000; B, x52 000. (arroiw, enchymal elements other than fibrosarcoma. In 1991 Neuman and Fletcherl' described nine cases which they classified as malignant smooth muscle actin (SMA) (dilute(d 1 in mesenchymoma. Four of these were liposar- 1500; Sigma). Smooth muscle and otheir heter- coma combined with rhabdomyosarcoma aris- ologous elements were absent. ing in retroperitoneum or spermatic cord. Two Paraffin wax embedded tissue from relevant further cases contained liposarcoma, rhab- areas was reprocessed for electron microscopy. domyosarcoma and osteo/chondrosarcoma Ultrathin sections of epoxy resin bloci ks were (abdominal wall and retroperitoneum). More stained with uranyl acetate and lead citrate, recently, the concept of malignant mesenchy- and examined in an AEI electron micri oscope. moma as an entity has aroused some contro- Some tumour cells contained sarc,omeric versy and Evans et al' suggested that most neo- myfofibrils (fig 2). These comprisedI thick plasms for which this diagnosis might be myosin filaments with dense bodies comipatible considered should be more meaningfully and with Z-disks. Thin filaments were also Ipresent specifically classified according to the predomi- but were not well preserved. nant component. They urged that the term Follow up revealed multiple bony mettastases malignant mesenchymoma be avoided where detected within three months of preserntation. possible. Conversely, Enzinger and Weiss8 The patient has subsequently received radio- seem to accept that tumours with myosarco- therapy to the groin. matous and liposarcomatous elements as true 772 Shanks, Banerjee, Eyden

malignant mesenchymomas but urge caution munohistochemically in all cases showing and application of strict diagnostic criteria in rhabdomyosarcomatous differentiation and order to avoid a "diagnostic wastebasket". This classified as malignant mesenchymoma.1' The J Clin Pathol: first published as 10.1136/jcp.49.9.770 on 1 September 1996. Downloaded from area is therefore obviously controversial and immunohistochemical and ultrastructural evi- our tumour could equally be regarded as a dence which we have presented confirms the malignant mesenchymoma as it would appear presence of rhabdomyoblasts in our case to meet the strict definition of that entity. Enz- beyond all doubt. This phenomenon might be inger and Weiss suggest classifying such a more frequent in liposarcoma than is generally tumour as malignant mesenchymoma, stating realised. the predominant tissue elements which in our case would be "malignant mesenchymoma We are grateful to Dr I Seddon of the Royal Oldham Hospital (combined myxoid and pleomorphic liposar- for allowing us to describe this case. coma with focal rhabdomyosarcomatous differentiation)". In this paper we have preferred 1 Evans HL, Khurana KK, Kemp BL, Ayala AG. Heterolo- to classify the tumour according to the predom- gous elements in the dedifferentiated component of dedif- inant component present as the rhabdomyosa- ferentiated liposarcoma. Am J Surg Pathol 1994;18:1150-7. 2 Evans HL. Smooth muscle in atypical lipomatous tumours. rcomatous elements were only present focally. A report of three cases. Am J Surg Pathol 1990;14:714-18. This approach has also been taken by others.4 3 Salanzo RP, Tomkiewicz Z, Africano WA. Dedifferentiated liposarcoma with features of rhabdomyosarcoma. Conn The clinical significance ofheterologous ele- Med 1991;55:200-2. ments is unknown but myxoid or pleomorphic 4 Tallini G, Erlandson RA, Brennan MF, Woodruff JM. Divergent myosarcomatous differentiation in retroperito- liposarcoma alone or in combination each have neal liposarcoma. Am J Surg Pathol 1993;17:546-56. potential for metastasis (as occurred in our 5 McCormick D, Mentzel T, Beham A, Fletcher CDM. Ded- case) as well as local recurrence.7 It has been ifferentiated liposarcoma. Clinicopathologic analysis of 32 cases suggesting a better prognostic subgroup among tentatively suggested that the presence of pleomorphic sarcomas. Am J Surg Pathol 1994;18:1213- heterologous elements in liposarcoma in itself 23. 6 Trojani M, Contesso G, Coindre JM, Coindre JM, Rouesse probably does not alter the prognosis.' J, Bui NB, et al. Soft tissue sarcomas of adults: study of Immunohistochemical confirmation of pathological prognostic variables and definition of a histopathological grading system. Int J Cancer 1984; rhabdomyosarcomatous differentiation in pre- 33:37-42. viously described examples of liposarcoma has 7 Evans HL. Liposarcoma. A study of 55 cases with a reassessment of its classification. Am J Surg Pathol been limited and electron microscopy has only 1979;3:507-23. been performed in one previous case.4 Myo- 8 Enzinger FM, Weiss SW (eds). Liposarcoma. In: Soft tissue tumors. St Louis: Mosby, 1995:431-66. globin reactivity was found in the three cases 9 Stout AP. Mesenchymoma, the mixed tumour ofmeschymal tested and myosin in one case tested. No other derivatives. Ann Surg 1948;12:278-90. skeletal muscle 10 Newman PL, Fletcher CDM. Malignant mesenchymoma. markers had been reported Clinicopathologic analysis of a series with evidence oflow- previously. Myoglobin was demonstrated im- grade behavior. Am J Surg Pathol 199 1;15:607-14. http://jcp.bmj.com/

_7 Clin Pathol 1996;49:772-773 Pseudopyropoikilocytosis: a striking artefact on September 24, 2021 by guest. Protected copyright. B J Bain, R Liesner

Abstract The blood films of patients with hereditary The blood films both of patients with pyropoikilocytosis show some resemblance to hereditary pyropoikilocytosis and ofthose the films of patients with severe burns.' This with severe thermal burns are character- observation led to the recognition of the ther- ised by budding erythrocytes and the mal instability of the red cell membrane which presence of microspherocytes. Recently, a characterises this condition. We have recently fourth example of similar morphological seen our fourth case of an artefactual change features, caused by overheating of a blood which simulates hereditary pyropoikilocytosis specimen in a motor vehicle during trans- and thus can cause diagnostic confusion. port to the laboratory, has been observed. A routine antenatal screening specimen from Department of It is important to be aware of this artefact an African woman who was 26 weeks Haematology, pregnant St Mary's Hospital as failure to recognise it is likely to lead to was received in our laboratory on an April Medical School, diagnostic confusion and unnecessary fur- afternoon. An automated full blood count on a Norfolk Place, ther testing, causing inconvenience to the Technicon H.2 counter gave the following London W2 1PG patient. results: white blood cell count 11.8 x 109/1; red Correspondence to: (7 Clin Pathol 1996;49:772-773) blood cell count 3.85 x 1012/1; haemoglobin Dr B J Bain. Keywords: pseudopyropoikilocytosis, artefactual results 10.6 g/dl; haematocrit 0.32; mean corpuscular Accepted for publication of laboratory tests, automated blood counters, erythro- volume 83 fl; mean corpuscular haemoglobin 21 February 1996 cyte morphology. 27.4 pg; mean corpuscular haemoglobin con-