Stephen Weiss

Two hundred and two benign and malignant soft tissue lesions were studied for the presence of S-100 protein by means of the peroxidase-antiperoxidase technique on formalin-fixed, paraffin-embedded tissue. Virtually all benign nerve sheath tumors (neurofibroma, neurilemoma, and granular cell tumor) contained numerous immunoreactive S-100-positive cells. Only one-half (18 of 36) of malignant schwannomas contained the protein, suggesting that its presence is an expression of differentiation in Schwann cell tumors. S-100 protein was not identified within pure neuroblastic tumors (neuroblastoma, neuroepithelioma) but could be identified within rare cells of the ganglioneuroblastoma and within the Schwann cell component of ganglioneuroma. It was also identified within most melanocytic tumors (cellular blue nevus, clear cell sarcoma, and melanoma). In fact, its constant presence in melanoma indicates that it may prove to be an independently reliable method for diagnosing amelanotic forms. It is also sporadically present within a variety of mesenchymal lesions including lipoma, liposarcoma, synovial chondromatosis, chondrosarcoma, fibromatosis, histiocytosis X, and chordoma. Although S-100 protein is highly characteristic of neural crest-derived tumors, it is not restricted to them and, consequently, must be interpreted cautiously. It may prove helpful in select situations such as the distinction of (a) benign nerve sheath tumors from other benign mesenchymal tumors such as fibrous histiocytomas, (b) cellular neurilemomas from malignant schwannomas, (c) malignant schwannomas from conventional fibrosarcoma (d) malignant melanomas from many carcinomas, and, possibly (e) juvenile xanthogranulomas from histiocytosis X.

Twenty-six cases of a newly recognized form of vascular tumor are presented. The tumor may occur at any age, has a male predominance, and develops preferentially in the dermis and subcutaneous tissues of the distal extremities. Histologically it combines the features of both a cavernous hemangioma and Kaposi's sarcoma. It is composed of thin-walled cavernous vessels which may be dilated, partially collapsed, or filled with organizing thrombi and phleboliths. These areas are intimately associated with spindled areas reminiscent of Kaposi's sarcoma. The spindled areas differ from Kaposi's sarcoma by the presence of occasional epithelioid endothelial cells, which sometimes display vacuolization. Follow-up information in 14 cases indicates that nine patients experienced "recurrences." One patient, who also received radiotherapy, developed regional lymph node metastasis 40 years after diagnosis and following 19 recurrences. No patient, however, has died of his disease, despite relatively limited surgical excision. The term "spindle cell hemangioendothelioma" is suggested for this vascular tumor of low-grade malignancy.

Described by Bednar as a "storiform neurofibroma," pigmented dermatofibrosarcoma protuberans is a rare neoplasm accounting for approximately 1-5% of all cases of dermatofibrosarcoma protuberans (DFSP). The lesion commonly presents as an exophytic, multinodular neoplasm of the dermis or subcutaneous tissue. It occurs predominantly in blacks. The majority are located on the trunk, and the remainder are more or less equally distributed in the upper and the lower extremities and the head and neck. Microscopically the lesion is characterized by spindled cells arranged in a tight storiform pattern and admixed with a small population of melanin-containing dendritic cells. The dendritic cells are the primary feature distinguishing this lesion from conventional DFSP. Three cell populations are identifiable by electron microscopy. The majority of cells resemble fibroblasts. A second population of cells exhibits long slender cell processes partially or completely invested by basal lamina. The third population of cells, also invested by basal lamina, contains both melanosomes and premelanosomes. The histogenesis of this neoplasm remains controversial. Although Bednar considered these lesions as variants of neurofibroma, S-100 protein could not be identified, and this finding contrasts significantly from the description of conventional neurofibroma, which almost always contains this antigen. Follow-up information available in nine cases indicates that this lesion may recur locally. Although distant metastases were not observed in our material, complete excision in conjunction with close follow-up care is indicated for this neoplasm of probable intermediate malignant potential.

We report 51 cases of a previously undescribed tumor of the distal extremities that is often mistaken for an inflammatory or infectious process, Hodgkin's disease, or various sarcomas. These lesions developed in patients of all ages (range, 4-81 yr; median, 40 yr) and affected the sexes nearly equally (27 men, 24 women). They presented as a painless mass of the fingers (14 cases), hand (11 cases), wrist or arm (10 cases), toe or foot (8 cases), or lower leg (5 cases), usually within the subcutaneous tissues. Grossly, they were infiltrative, multinodular masses characterized by a dense chronic inflammatory infiltrate that merged with a stroma, which varied from densely hyaline to focally myxoid and contained sheets of short spindled to rounded epithelioid cells. Focally, the epithelioid cells were extremely large with bizarre, vesicular nuclei and macronucleoli resembling Reed-Sternberg cells or virocytes. Despite the level of atypia, mitotic activity was low. The tumor cells consistently expressed vimentin but lacked a variety of other mesenchymal, epithelial markers, e.g., S100 protein, desmin, actin, neuron-specific endolase, epithelial membrane antigen, HMB-45, CD34) and leukocyte markers (CD15, CD30, CD45). Keratin was noted focally and weakly in four cases and CD68 focally in six cases, the latter suggesting that the cells had acquired phagocytic properties. Immunostains for cytomegalovirus were negative. Polymerase chain reaction for Epstein-Barr virus showed amplification levels consistent with latent infection in 4 of 10 cases, but no cases showed levels consistent with active infection. All of the bacterial and viral cultures were negative. Follow-up information was available in 27 cases. Recurrences developed in six patients (interval, 15 mo-10 yr), but there were no metastases or tumor-related deaths. In one patient, progressive proximal extension up the arm was noted. Although the most common submitting diagnosis was that of an inflammatory or infectious process, the negative studies for infectious agents, clinical behavior with local recurrences, immunophenotypic profile, and cytologic atypia support the idea that these are unusual mesenchymal neoplasms with at least the potential for local recurrence. It remains to be investigated whether with time these lesions will prove to have metastatic potential.