Quiz 58: What is your diagnosis?

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Diagnosis: Quiz 58

Quiz 58

Answer: "Small-plaque parapsoriasis" and "large-plaque parapsoriasis" (superficial expressions, i.e., macules and patches, of mycosis fungoides)

Criteria for diagnosis clinically: Slightly scaly, poorly-circumscribed, dull red patches are those of expressions of mycosis fungoides termed "small-plaque parapsoriasis" and "large-plaque parapsoriasis."

Differential diagnosis clinically: Unlikely is the possibility of psoriasis, but in order to exclude that inflammatory disease definitively, performing a biopsy is reasonable.

Criteria for diagnosis histopathologically: The changes of a sparse superficial perivascular infiltrate of lymphocytes, a patchy infiltrate of lymphocytes in company with coarse bundles of collagen in haphazard array, a few lymphocytes disposed as solitary units in the basal layer of the epidermis and others scattered in loci of the spinous zone in conjunction with scant spongiosis, as well as the presence of elongate mounds of parakeratosis, sum to a diagnosis of mycosis fungoides.

Differential diagnosis histopathologically: There is none. 

Clinicopathologic correlation: The patches are a consequence of the infiltrates of lymphocytes, they are dull red because venules and capillaries in the upper part of the dermis are dilated widely and, in vivo, the lumen of them were jammed with erythrocytes, and the scale is a manifestation of the elongate mounds of parakeratosis.

Options for therapy predicated on knowledge of histopathologic findings: Because the infiltrate of lymphocytes is so superficial, being present in the uppermost part of the dermis and in the epidermis, lesions such as these respond to application topical of a fluorinated corticosteroid or to treatment with PUVA or UVB.

1) What for nearly 70 years was termed "large-plaque parapsoriasis" is now recognized universally to be mycosis fungoides. To this day, however, no standard textbook of dermatology, general pathology, or dermatopathology states unambiguously that small-plaque parapsoriasis also is mycosis fungoides-but it is-and the lesions in this patient demonstrate that convincingly. Once that reality is acknowledged, there is certain to be an "epidemic" of mycosis fungoides, just as the one alleged currently for melanoma-and for the very same reasons: far better criteria, clinical and histopathologic, for diagnosis of flattish lesions of them and far better surveillance of patients.

2) The teaching in dermatology for generations was that "large-plaque parapsoriasis" was not  mycosis fungoides but rather that condition in 5 to 10% of patients could "transform" into mycosis fungoides. In reality, both "large-plaque parapsoriasis" and "small-plaque parapsoriasis" are, from the very outset mycosis fungoides, just as solar keratosis and Bowen's disease, from the very beginning, are squamous-cell carcinoma, neither, ever, "transforming" into squamous-cell carcinoma because they are that from the get-go.

3) Features clinical could, conceivably, be confused for an unusual presentation of psoriasis, but findings histopathologic shown here are diagnostic of mycosis fungoides. That being the case, a histopathologist should not shrink from issuing a diagnosis of mycosis fungoides. A clinician should understand full well that "large-plaque parapsoriasis" and "small-plaque parapsoriasis" are but two of many variations morphologic of a systemic lymphoma, mycosis fungoides, other manifestations of it being alopecia mucinosis, granulomatous slack skin, and Sezary syndrome, as well as stereotypical plaques, nodules, and tumors, some of which may become ulcerated.

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