Quiz 22: What is your diagnosis?

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Diagnosis: Quiz 22

Quiz 22

Answer: Basal-cell carcinoma

Criteria for diagnosis clinically: An ill-defined, violaceous plaque with an ever so slight tinge of orange, marked in its center by a large hemorrhagic crust is consonant with one expression of basal-cell carcinoma.

Differential diagnosis clinically: This could be a process infectious, such as one induced by an atypical mycobacterium or another type of inflammatory process, such as a lesion of impetiginized nummular dermatitis secondary to excoriation. Also to be considered is another malignant neoplastic process, such as an amelanotic melanoma. Biopsy is essential if the character fundamental of it is to be determined.

Criteria for diagnosis histopathologically: An asymmetrical neoplasm, in the upper part of the dermis made up of aggregations of abnormal trichoblasts ("follicular" germinative cells) arranged in solid masses, variable in size and shape, seated beneath shallow ulcers covered by hemorrhagic scale-crusts represents a basal-cell carcinoma of the type designated "nodular."

Differential diagnosis histopathologically: There is none.

Clinicopathologic correlation: The plaque is formed mostly of neoplastic germinative cells, but also of a patchy infiltrate of inflammatory cells. The purple hue resulted from numerous venules in proximity close to the neoplasm having been dilated widely in vivo and there having been stuffed with erythrocytes. The hemorrhagic crust consists of serum and neutrophils, as well as countless extravasated erythrocytes. 

Options for therapy predicated on knowledge of histopathologic findings: A malignant neoplasm such as this one must be excised with sufficiently normal skin around it to ensure that that purpose has been achieved. As can be told at scanning magnification, that desideratum has been accomplished here.

1) The neoplastic cells that constitute a basal-cell carcinoma are abnormal trichoblasts, i.e., neoplastic cells of a type analogous to those present normally in an embryo at about 10 weeks, they at that time forming a crescentic mass situated at the base of surface ectoderm. The cells of that germ, i.e., germinative ones, in succeeding weeks of embryogenesis give rise to the entire infundibulo-apocrine-sebaceous-follicular unit. Rather than name that germ for all four structures to which it gives rise, that being unwieldy, we refer to it simply as "follicular germ."

2) Because of the character basic of neoplastic trichoblasts, a basal-cell carcinoma has capability, in theory, to differentiate along infundibular, apocrine, sebaceous, and follicular lines. Very uncommonly does that happen in a manner so definitive as to be identifiable by conventional microscopy. Sometimes small infundibulocystic structures punctuate aggregations of a basal-cell carcinoma. Rare in the extreme do solid masses contain tubules that resemble those of an apocrine duct, and hardly ever is there formation of glandular structures that show signs of "decapitation (apocrine) secretion." Sebocytes also are met with rarely in a basal-cell carcinoma, and true follicular structures, such as a well-formed bulb and a contiguous papilla or trichohyalin granules and/or blue-gray corneocytes of inner sheath, are encountered rarely, too. Not uncommonly, however, follicular germ-like structures unaffiliated with a follicular papilla are present, sometimes in large number, in a basal-cell carcinoma.

3) Because a basal-cell carcinoma is made up of neoplastic trichoblasts, we think of it as being a "trichoblastic carcinoma," the malignant equivalent of trichoblastomas (e.g., trichoepithelioma, desmoplastic trichoepithelioma, adamantinoid trichoblastoma, etc.). In practice, we refer to the neoplasm as "basal-cell carcinoma" while recognizing, full well, how uninstructive that designation is in regard to the rudimentary nature of the neoplastic cells.

4) At the lateral margins of this basal-cell carcinoma are signs incontrovertible in the upper part of the dermis of changes secondary to severe stasis, namely, a seemingly marked increase in the number of venules and capillaries typified by a thick wall and plump endothelial cells. Those changes can be seen in the last series of photomicrographs to be associated with fibrosis like that of a scar, the fibroplasia being a consequence of effects long-standing of marked stasis.

5) The basal-cell carcinoma pictured clinically in no way resembles the stereotype of it that is taught to medical students and residents in dermatology. In fact, it is impossible, on grounds clinical alone, to make a diagnosis with certainty of basal-cell carcinoma here. That particular kind of carcinoma is extraordinarily protean in the manner in which it presents itself clinically, the lesion in this patient being but one example of that diversity. The same statement can be made for all maladies of the skin, including those non-neoplastic.

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