Invisible Dermatoses To our knowledge, Martin Brownstein and tle else besides a cornoid lamella. Multiple Asher Rabinowitz first used the term "invisi- sections must be searched to find this struc­ ble dermatoses."* Generations of dermatolo­ ture (p. 176). gists, however, have struggled with biopsy 3. Ichthyosis-Often the only clue to ich­ specimens from diseased skin that appear to be thyosis vulgaris is the absence of a granular normal under the microscope. Since normal layer that is associated with compact hy­ skin is rarely ever biopsied in clinical practice, perkeratosis. In the absence of hyperkera­ one must assume that some disease is present. tosis, this is an easy diagnosis to miss. Technical problems must be eliminated, such 4. Pigment changes-Vitiligo looks almost as sampling errors where normal skin on an normal, except that melanocytes are miss­ edge of the biopsy specimen has been sectioned ing (as is melanin). Conditions that have in­ and the diseased tissue has been left in paraf- creased melanin, but normal numbers of fin. It is wise to check again to see if the cli­ melanocytes (e.g., freckles and cafe au lait nician might have submitted normal skin (e.g., spots) may be mistaken for normal black pruritus, resolved urticaria, patient insisting skin. that normal spot is painful, and normal skin obtained for IF but submitted for H&E stain­ ing). At this point, one needs a strategy for studying skin that appears histologically nor­ Dermal Diseases mal, but must contain disease. We consider the following conditions: 1. Incontinence of pigment-Melanin in the papillary dermis may be the only clue to a der­ matitis that involved the epidermal-dermal Epidermal Diseases junction (e.g., lichen planus or lupus erythematosus ). 2. Amorphous deposits in the papillae-Ma­ 1. Tinea versicolor and fungal disease­ cular amyloidosis can have very subtle deposits Check the stratum corneum for hyphae and of amyloid in the dermal papillae; other forms do a PAS stain. of cutaneous amyloidosis may have deposition 2. Porokeratosis-Porokeratosis may have lit- around blood vessels. Special stains for amy­ loid will help. *Brownstein MH, Rabinowitz AD: The invisible 3. Mast cell infiltrates (p. 161)-Mastocyto­ dermatoses. J Am Acad Dermatol 8:579-588, mas are easy to identy, but both urticaria pig­ 1983. mentosa and telangiectasia macularis eruptiva 209 210 Invisible Dermatoses perstans may have only slightly increased long axis traverses the border between diseased numbers of mast cells. Eosinophils, increased and normal skin or by studying punch biopsy pigment, and increased vessels are adjunctive specimens from diseased and contralateral clues. normal skin (the latter would then, by defini­ 4. Dermal melanocytes-Sometimes, the de­ tion, be an invisible dermatosis if misfiled or position of dermal spindle-shaped melanocytes transposed). in a blue nevus can be quite subtle. In the more Macular atrophy, or anetoderma, is defined diffuse dermal melanocytic conditions (e.g., by the absence of elastin with normal collagen; Mongolian spot in the neonates), it often is im­ in atrophoderma, however, the dermis is sim­ possible to find the melanocytes. ply reduced in thickness, but contains normal 5. Argyria-A patient may be almost silver­ elastin and collagen. Both present as depres­ black clinically with cutaneous silver deposits sions; thus, a careful biopsy procedure, com­ and still have only subtle grains of silver about parison with normal skin, and use of special dermal sweat ducts histologically. Always ex­ stains all are required for an accurate diagno­ amine the basement membrane zone around sis. In focal dermal hypoplasia, the dermis also sweat ducts in otherwise normal skin. is thinned, but to such an extent that the di­ 6. Urticaria-Urticarial lesions often may agnosis is obvious. Connective tissue nevus (or show only minimal edema with a sparse peri­ the shagreen patch in tuberous sclerosis) has vascular lymphocyte infiltrate. Sometimes, a an excess of elastin, collagen, or both. Once resolving urticarial lesion will be normal or a again, only comparison within normal skin and true invisible dermatosis. use of special stains will allow a diagnosis. 7. Connective tissue-Connective tissue ab­ There are many other examples of invisible normalities can be very subtle; here, it often is dermatoses; hopefully, however, these few dis­ necessary to compare normal and abnormal ease entities will give the beginner a means of structures either by studying an ellipse whose approaching the problem. Further Readings Walter H. C. Burgdorf As mentioned in the introduction, this book (As mentioned on p. 57, Dr. Ackerman's was produced without references to help main­ book gives a sense of order to the befuddling tain its simple format. I hope that every reader world of inflammatory skin disorders. I will have access to at least one additional der­ highly commend both his approach and his matopathology textbook and will consult it book.) often; both for further information and for ref­ Ackerman AB, Niven J, Grant-Kels JM: Dif­ erences. This annotated reading list is selec­ ferential Diagnosis in Dermatopathology. tive-not inclusive. Hopefully it provides an Lea & Febiger, Philadelphia, 1982, 195 pp. adequate introduction to the literature of (The format of this effort is unique. Dr. Ack­ derma topa thology. erman and his coworkers contrast 45 pairs of difficult histologic diagnoses, such as Pa­ STANDARD TEXTBOOKS get's disease versus Bowen's disease, with Lever WF, Schaumberg-Lever G: Histopath­ color pictures and lists of diagnostic ology of the Skin. JB Lippincott, Philadel­ criteria.) phia, 1983, 848 pp. (Dr. Lever's book is the classic text with the Enzinger FM, Weiss SW: Soft Tissue Tumors. best references. I cannot imagine studying a The CV Mosby Co, St. Louis, 1983, 840 pp. microscopic slide or writing about skin pa­ (Dr. Enzinger and Dr. Weiss have produced a masterpiece; readable, but unquestion­ thology without a copy at my side.) ably authoritative. Dermal proliferations, Pinkus H, Mehregan AH: A Guide to whether neural, muscular, vascular, or fibro­ Dermatohistopathology. Appleton-Century­ blastic, are reviewed in depth; but, in a prac­ Crofts, New York, 1981,591 pp. tical fashion.) (If you canfind an older edition of this text, buy it. Dr. Pinkus was among the first to em­ McGovern VJ: Melanoma: Histological Diag­ phasize correlation of skin anatomy and dis­ nosis and Prognosis. Raven Press, New ease, an embryologic approach to appenda­ York, 1983, 197 pp. geal tumors, and pattern diagnosis. In later Roses DF, Harris MN, Ackerman AB: Diag­ editions, his text has become more diffuse nosis and Management of Cutaneous Ma­ and encyclopedic.) lignant Melanoma. WB Saunders, Philadel­ phia, 1983, 304 pp. OTHER BOOKS (Malignant melanoma is, at once, the most Ackerman AB: Histologic Diagnosis of In­ important single topic in dermatology and a flammatory Skin Diseases. Lea & Febiger, most difficult subject to adequately cover in Philadelphia, 1978, 863 pp. an introductory textbook. These two new 211 212 Further Readings books have been most helpful to me in trying ology papers appear in the following journals: to keep abreast of this crucial area.) American Journal of Surgical Pathology Archives of Dermatology PERODICALS British Journal of Dermatology No textbook can be up to date; something is Cancer always new in the literature. Two journals are Histopathology devoted specifically to dermatopathology: Journal of the American Academy of American Journal of Dermatopathology Dermatology Journal of Cutaneous Pathology Once again, other valuable dermatopathology These two journals, however, have not cap­ articles appear outside of this short list; how­ tured the market as far as quality skin pathol­ ever, if you read the above journals, you will ogy articles. Many outstanding dermatopath- rarely be too far behind in studying skin. Glossary This glossary is highly restricted; it only in­ Buckshot scatter: Random distribution of cludes those dermatopathologic terms that are melanocytes through epidermis in malignant used in the histologic descriptions in this man­ melanoma. ual. Many important expressions have been omitted simply because of the limited size of Cartwheel pattern: Spindle-shaped tumors the text. Furthermore, no attempt has been may be arranged so that the elongated cells ra­ made to define normal structures or diseases; diate from a central point like a cartwheel. these subjects are listed in the index. Caseation necrosis: Total necrosis, initially described in tuberculosis; histologically, one Abscess: Accumulation of neutrophils. sees no remnants of cell structures, just ne­ Acantholysis: Loss of adhesion between epi­ crotic material. dermal cells. Civatte body: Degenerated keratinocyte, Acanthosis: Thickening of epidermis because which appears homogeneous and eosinophilic; of increased number of keratinocytes (see common in lichen planus. Hypertrophy). Collarette: A little collar; refers to a periph­ Atrophy: Condition of being flattened or eral process, such as scale about a lesion or an thinned; most often refers to a thinned layer, epidermal reaction about a tumor, or such as such as epidermis or dermis. the epidermis encompassing the metastatic Atypia: Cytologic abnormality of cells, with malignant melanoma (p. 138). abnormal irregularly shaped nuclei and mi­ Colloid body: See Civatte body. toses; suggesting a malignant change. Cornoid lamella: Parakeratotic column in porokeratosis. Ballooning degeneration: Epidermal change