Quiz 48: What is your diagnosis?

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Diagnosis: Quiz 48

Quiz 48

Answer: Dermatofibrosarcoma protuberans

Criteria for diagnosis histopathologically: A proliferation of oval, spindle-shaped, and wavy fibrocytes in haphazard array and affiliated with delicate fibrillar bundles of collagen that extend from the papillary dermis throughout the reticular dermis and into a septum of the subcutaneous fat at the base of the section is that of dermatofibrosarcoma protuberans.

Differential diagnosis histopathologically: There really is none, although some similarities can be noted with the dermatofibroma shown in the photomicrographs at the outset of Quiz 723. Not only is there a proliferation of mesenchymal cells in company with thin bundles of altered collagen in both conditions, but the epidermis is hyperplastic and hyperpigmented. Nonetheless, the wavy character of the nuclei of the cells constituent, the involvement of a septum in the subcutaneous fat whose trabecular character is preserved still, and the absence anywhere at the periphery of fibrocytes splayed between thickened bundles of collagen militate against dermatofibroma for the process pictured in these photomicrographs. Because of the combination of wavy nuclei of fibrocytes and wavy bundles of collagen, this lesion could be misconstrued as a benign neoplasm with neural differentiation, but that possibility is excluded by its failure to fulfill criteria for neurofibroma, schwannoma, or any established presentation of neuroma. Moreover, it qualifies histopathologically as a dermatofibrosarcoma protuberans.

Criteria for diagnosis clinically: An ill-defined, peculiarly-shaped brown plaque tinged with violaceous and orange hues made up of contiguous smooth-surfaced papules of different sizes and heights is a dermatofibrosarcoma protuberans.

Differential diagnosis clinically: There is none.

Clinicopathologic correlation: The plaque is formed of the sarcoma present throughout the dermis and in the septa especially of the subcutaneous fat; the "individual" papules are accounted for by the distinct papillations histopathologic; the brown cast is a result of an increase in amount of melanin in the hyperplastic epidermis; the violaceous/orange is a consequence of the combination of an increase in epidermal melanin and an increase in dermal blood by virtue, in vivo, of superficial small vessels having been dilated and filled with erythrocytes; and the smooth surface signifies a cornified layer normal.

Options for therapy predicated on knowledge of histopathologic findings: Awareness, acutely, of the histopathologic lateral and deep margins of dermatofibrosarcoma protuberans virtually always being ill-defined should telegraph rightly to a surgeon that a substantial zone of skin and subcutaneous tissue deemed clinically to be "normal" must be excised if the sarcoma is to be extirpated once and for all. All too often, a surgeon fails to remove sufficient truly normal tissue all the way around a dermatofibrosarcoma protuberans, the inevitable result being persistence of the malignant neoplasm at the local site.

Unlike the situation for melanoma (with the exceptions of amelanotic melanoma and desmoplastic/neurotropic melanoma) in which a narrow margin of normal skin suffices for excision in toto, that is not the case for those malignant neoplasms poorly circumscribed, the most notorious of those in that regard being angiosarcoma, extramammary Paget's disease, morpheiform basal-cell carcinoma, microcystic adnexal carcinoma, and dermatofibrosarcoma protuberans. What often appears to be clinically "normal" skin to a surgeon actually is tissue containing cells malignantly neoplastic.

1) The findings histopathologic shown here are not stereotypical of those in a dermatofibrosarcoma protuberans developed fully, the latter being typified by fascicles that intersect one another in a manner that has been dubbed "cartwheel," "pinwheel," and "whirligig," three descriptive terms that convey a sense for motion that never is actually discernible in a section of tissue scrutinized through a microscope conventional. 

2) The changes histopathologic in the second biopsy specimen taken from this dermatofibrosarcoma protuberans are much more advanced than those in the first biopsy specimen. In it, elongate fascicles cellular highly interweave in pattern storiform, that appearance being absent from the section of tissue cut from the first biopsy specimen. Sometimes, sections of tissue from a specimen of dermatofibrosarcoma protuberans display nary a single fascicle, but rather messenchymal cells with wavy nuclei scattered in a sea of mucin within which are distributed delicate fibrillar bundles of collagen.

3) Note carefully the monomorphic quality of the nuclei of the constituent mesenchymal cells and the absence of mitotic figures from this sarcoma, an illustration, once again, of the disparity met with from time to time between characteristics cytopathologic and behavior biologic. Nuclei of a benign neoplasm, such as Spitz's nevus, can be rivetingly abnormal, i.e., very large, strikingly pleomorphic, and distinctly heterochromatic, and the same can be said for nuclei in that inflammatory process known as "dermatofibroma with 'monster' cells." In contradistinction, nuclei of cells constituent of sarcomas, such as those of dermatofibrosarcoma protuberans, the macule/patch stage of mycosis fungoides, and even some examples of primary cutaneous melanoma, may be small and monomorphic. As a rule, the nuclei of renal-cell carcinoma metastatic to skin tend to be small and monomorphic.

4) Just how poorly delineated are the boundaries of dermatofibrosarcoma protuberans is revealed graphically in both biopsy specimens, the neoplastic cells extending to both lateral margins and to the base of the first specimen and to one lateral margin of the second.

5) There is a tendency on the part of some general pathologists to confuse "dermatofibroma" with "dermatofibrosarcoma protuberans." That bewilderment stems, in part, from the similarity in nomenclature, neoplasia is attributed wrongly by them to dermatofibroma because of the misperception of the suffix  -oma, signifying a tumor, and the deeply flawed concept that some dermatofibromas have metastasized, which never has happened, ever, because dermatofibroma is a type of fibrosing inflammation. Basics such as these should be taught in textbooks of general pathology and soft tissue pathology, instead of the humbug currently propagated unashamedly.

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