AMF (S1C14t3P1)

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Fig. c14t3P1: The lesion, in what might be characterized as typical patterns, is polypoid at the surface of the skin. It appears to be a tumor of the papillary dermal connective tissue. It is circumscribed and expansile. At the deep margin, a condensation of fibrous tissue, at the interface between the tumor and the reticular dermis, is represented. The lesion is cellular, but scattered lytic defects are represented. Focally, it extends close to the dermal-epidermal interface. The overlying epidermis is acanthotic, and shows effacement of the rete ridges. There is a suggestion of a collarette at the lateral margins. The biopsy is superficial.

Fig. c14t3P2: This is a second example; the patterns are similar but, focally, cells are loosely spaced in a pale, myxoid matrix.

Fig. c14t3P3: There is much about this lesion to compare with the patterns of the lesions of figs. 1 & 2. In this example, the tumor forms a column that pushes into the dermis and the subcutaneous fat. A thin condensation of fibrous tissue outlines the tumor. The lesion is uniformly cellular. It is composed of closely spaced, stellate-shaped, fibroblastic cells in a delicate myxomatous matrix. It might be argued that this is a distinctive lesion other than an adventitial myxofibroblastoma, but this may represent extension of tumor along a perifollicular connective sheath (a component of the adventitial dermis). The alternative would be to characterize the lesion as a cellular myxoma.

Fig. c14t3P4: In this cellular component, basic cytologic features are  represented. The close spacing of cells in a scanty matrix provides an epithelioid quality. Tumor cells are polygonal or rounded; they have rounded nuclei with marginated chromatin and a central nucleolus. The cytoplasm of each rounded cell is lavender. Among these tumor cells are smaller cells with the nuclear characteristics of histiocytes; the nuclei of these cells are elongated, and have delicate nuclear chromatin. Some of the nuclei of histiocytes are grooved; some of the nuclear characteristics are reminiscent of the nuclei of the cells of histiocytosis X (“Langerhans histiocytosis”). There is little evidence of a fibrous stromal component; the cells are back to back in a mucinous stroma. A cell to the left of the center of the field is larger than its neighbors. Its nucleus is somewhat eccentric, and has dense chromatin. It is well defined at the cell membrane level. There is a central area of cytoplasm that is acidophilic. The periphery of the cytoplasm is clear and mucinous (a quality not easily appreciated in this photo). There are spidery extensions of cytoplasm from the acidophilic zone into the mucinous zone. Such cells, if identified in the tumor, are a great aid in diagnosis.

Fig. c14t3P5: In areas, tumor cells are plump and tend to form whorls. The plump cells ( and the other tumor cells) tend to have lavender cytoplasm. The plump cells, in the tight whorls, are molded against their neighbors. Small vessels are distributed among the whorls (glomus-like?).

Fig. c14t3P6: Plump, lavender tumor cells are clustered to form a whorl in the center of the field. In the whorl, some of the cells are loosely spaced in a delicate fibrous matrix. This may represent a tangential section of a distinctive vessel. The lavender cytoplasm is not a characteristic of a common histiocyte. Lavender cytoplasms generally correlate with cells that are rich in endoplasmic reticulum, and are engaged in anabolic rather than catabolic functions.

Fig. c14t3P7: This is a lesion showing a fibrous matrix among tumor cells, particularly in the left lower corner of the field; in this area, cells are spindle shaped and loosely spaced in a delicate fibrous matrix. In the center of the field, angulated defects represent zones of cytolysis. Cells loosely spaced in the defects are mostly KP-1 + histiocytes. To the right near the bottom of the field, a distinctive vessel with a thick, fibrous wall is represented. Tumor cells are individually isolated in the wall of this vessel. These vascular changes are an additional aid in diagnosis.

Fig. c14t3P8: In this area, a lytic defect is represented to the extreme left of the field. Generally, cells are loosely spaced in a pale myxoid matrix. Cells are spindle and stellate in outline. There are occasional, small multinucleated giant cells. Small lavender arrows point to distinctive myxoid, epithelioid cells of the tumor. These distinctive cells identify this variation in pattern as being within the spectrum of adventitial myxofibroblastoma.

Fig. c14t3P9: This lesion shows a prominent fibrous matrix in which individual tumor cells are isolated. The cells are mostly stellate in outline; they resemble fibroblasts commonly seen in “fibroblastomas.” To the left, epithelioid cells cluster about vessels in a distinctive pattern: this preponderantly fibrous lesion belongs in the category of adventitial myxofibroblastoma; the clustered, distinctive epithelioid cells establish the category to which this lesion is properly assigned. The tinctorial qualities of the cytoplasm of the tumor cells are distinctive; glomus cells do not display similar qualities. Myoid cells might show similar qualities but the immunohistochemical findings do not identify the cells as myoid (myopericytes).

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