Journal of Cutaneous Pathology

1977:4:9-13

Pigmented Storiform Neurofibroma DANIEL .1. SANTA CRUZ' AND ALLAN .1. YATES^ 'Department of Pathology, Division of Surgical Pathology, Washington University, St. Louis, MO: 'Department of Pathology, Division of Neuropathology, The Ohio State University, Columbus, OH, U.S.A. A case of pigtitented storifortn neurofibroma (PSN) is presented. The lesion was present in the shoulder of a 7-year-old black girl and recurred after 10 years. The characteristic storiform pattern and melanin production are the relevant features for histologic diagnosis. The histogenesis and taxonomic position of this lesion is discussed with emphasis on its relationship with dcrmatofibrosarcoma protuberans (DI SP) and cellular blue nevus. (Received for publication November 26, 1976)

The pathologists's interest in the origins and interrelationships of tnelanin-containing tumors arises not only frotn the practical consideratiotis of their diagtioses, but also those concerning their histogeneses. In addition to the common neoplasms of the nevusmelanocyte, melanin-containing tutnots of elements derived frotn neural crest, which are usually non-pigmented, have been reported. Therefore, it has frequently been assutned that melanin within a tutnor is evidence that its origin is frotn a cell type derived ftom the neural crest. Thus the fitiditig of pigmented cells within an otherwise typical detmatofibrosarcotna protuberans (DFSP) (Hashimoto et al. 1974) or storifortn neurofibroma (Bednaf 1957) suggests a developmental relationship between these two tumors and others of neural crest origin. We have recently seen an example of such a pigmented tutnor which, because of its rarity and controversial histogenesis, warrants reporting and discussing. Case Report

Clinical History The patient is a black female who, at the age of 7 years, developed a slowly growing mass in the skin over her right shoulder. At 9 years

of age it was excised and the wound skingrafted. For lOVi years there was no evidence of recurrence, but at age 17 a rapidly-growing mass developed in the resection scar. There was no evidence of metastatic disease and the tnass was again excised and the skin grafted. It is now 12 months since the second procedure and there is no evidence of recurrence. Pathology The gross appearances of both specimens were sitnilar: 6 ctn tnasses covered with skin whieh on cross section was speckled with numetous small black regions. Microscopic examination of the first specimen revealed a very cellular tumor with tninitnal strotna which was separated frotn the epidermis by a grenz zone. It had no capsule and although the tumor cells had infiltrated the dertnis, and in places the subcutis, its borders were rather sharply delineated (Fig. 1). The cells composing the tutnor were of two types. The majority, which were uniform and spindle-shaped, were arranged in intertwining fascicles which in many areas cotnposed a storiform pattern (Fig, 2), The second type of cell contained, within its perikarial cytoplastn and long dendritic processes, a dark

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Fig I liorder of the lumor Note the pushing margin in the top ot tlie tigure and tlic melanin located mamly m dendritic cells. H & E X 90. (Wash. U. neg. 76-8233)

Fig. 2. C e n t r a l p o r t i o n of t h e t u m o r . N o t e t h e p r o m i n e n t s t o r i f o r m p a t t e r n and tlie sparsity of m e l a n i n

production. H & E X 90. (Wash. U. neg. 76-8234)

PIGMENTED STORIFORM NEUROFIBROMA

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Fig 3 Detail of the melanotic portion. The melanin is predominantly located within dendritic cells. H & E X 350. (Wash. U. neg. 76-8235) brown pigtnent, which stained positively with Fontana-Masson stain (Fig. 3). These were located among the fascicles and were tnost frequent at the periphery of the tumor. No mitotie figures were seen in either cell type; nor was there any pigtnent within the spindle cells or stromal histiocytes. The microscopic appearance of the recurretit lesion was sitnilar, but contained fewer melanin-eontainitig cells. Discussion

Two cell types which certainly arise frotn neural crest are the Schwann cell and nevusmelanocyte (Weston 1970). It is virtually certain that schwannomas, neutofibtomas and their maligtiant counterparts are derived from the former, and that nevi, blue nevi, cellular blue nevi and tnalignant rtielanomas are from the latter. However, tutnors with features of both nevus-tiielanocyte and Schwann cell occur. Although the mechan-

istns involved in the pathogenesis of this latter group are still debated (Nakai & Rappaport 1963, Spence et al. 1976), hypotheses to explain the histological features of the cell types within one tutnor usually invoke their comtnon neural crest origin (Mandybur 1974), The tnelanotic schwannoma (Hodson 1961, Shillitoe 1965), pigmented neurofibrotna (Bird & Willis 1969) and neuronevus are exatnples of such transitional tutnors. Several other tutnor types of neural origin which are usually not pigmented have also occasionally occurred with melanin (Limas & Tio 1972, McCloskey et al. 1976). The melanin-containitig cotnponents of these tutnors have also been assutned to be of neutal crest origin. There is less certainty as to the cell(s) of origin of tumors, such as the one in this case report, which were described and given the natne storifortn neurofibtotna by Bednaf (Bednar" 1957). He argued for a neural crest origin of this tutnor for three reasons. Firstly,

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the cells composing it appear on light microscopic examination to be very similar to Schwann cells. Secondly, a few examples of storiform neurofibroma have contained melanin. Thirdly, the same storiform pattern occasionally is seen in cellular nevi (Bednaf 1 970) and dermatofibrosarcoma protuberans (Hashimoto et al. 1974). However, the cell of origin of the latter tumor is not yet established, and results of electron mieroseopic studies on these have been interpreted as evidence both for a neural (Hashimoto et al. 1974)andhistiocytic(Ozello& Hamels 1976) origin. Nevertheless, as with the storiform neurofibroma, some cases of dermatofibrosarcoma protuberans have contained melanin. This strongly suggests that it is derived from neural crest and indicates that it is closely related to the storiform neurofibroma which, as in the tumor in this report, sometimes contains melanin. Thus melanotic forms of these two tumors have histological features of both the nevus-melanocyte and Sehwann cell lines, and both the pigmented storiform neurofibrosaroma and pigniented dermatofibrosarcoma protuberans should be classified along with the melanotic sehwannoma and neuronevus in a group transitional between those tumors derived solely from the Schwann cell or from the nevus-melanocyte. The non pigmented neurofibromas have ^ ^

strong ties to the neural tumors group and DFSP, while the PSN has remarkable morphological similarities to the cellular blue nevus, thus this tumor may represent the "lost link" to both groups and leads us to speculate on their possible histogenetic relationship among these lesions, based on morphological findings (Fig. 4). The sehwannoma and neurofibroma are almost certainly of neural cell origin as are their malignant counterparts neurofibrosarcoma and malignant schwannotna. Although less certain, it seetns that DFSP and storiform neurofibroma are probably of neural origin (Bednaf 1957, Hashimoto et al. 1974). On the other hand, the melanocytic-nevus cell origin seems quite certain for the different variants of nevi, blue nevi, cellular blue nevus and malignant melanoma. Act

Pigmented storiform neurofibroma.

Journal of Cutaneous Pathology 1977:4:9-13 Pigmented Storiform Neurofibroma DANIEL .1. SANTA CRUZ' AND ALLAN .1. YATES^ 'Department of Pathology, Di...
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