Seborreic keratosis with Bowenoid transformation.

Sir,

Seborrheic keratosis is a common benign skin tumor which usually appears in mid-adult life.[1] Though any part of the body may be affected, the common sites are trunk and face. The lesion can show a variety of histological appearances and seven types have been identified: (a) irritated, (b) adenoid or reticulated, (c) plane, (d) clonal, (e) melanoacanthoma, (f) inverted follicular keratosis, and (g) benign squamous keratosis. The most common is the acanthotic type.[2] Most of them are benign, but occasionally in situ carcinoma or the so-called Bowenoid transformation can take place in acanthotic type of seborrheic keratosis. It mostly occurs in sun-exposed areas of the skin.[2]

We report the case of a 59-year-old male patient who presented with an exophytic growth on the dorsal aspect of left hand since 8 years. Wide excision was done and tissue sent to pathology department with the clinical suspicion of Bowen's disease.

Specimen consisted of a piece of skin tissue measuring 5 cm in length with an exophytic growth on the surface which measured 0.5 cm. Figure 1 shows the clinical presentation of the lesion. Cut surface revealed gray brown discoloration. Microscopy of the lesion showed epidermis with hyperkeratosis and psoriasiform hyperplasia of rete ridges. Full-thickness atypia of rete ridge was also noted with loss of polarity of cells throughout the epidermis [Figure 2]. There was increased mitotic activity with atypical mitosis. Basement membrane was intact and subepithelial tissue showed dense mononuclear infiltrates [Figure 3]. A few horn cysts were also seen. A diagnosis of seborrheic keratosis with Bowenoid transformation was made.

Figure 1

Clinical appearance of the lesion

Figure 2

Microphotograph depicts hyperkeratosis, and psoriasiform hyperplasia of rete ridges with full-thickness hyperplasia

Figure 3

Microphotograph showing increased mitotic activity in the rete ridge and mononuclear cell infiltrates in the subepithelial tissue

Seborrheic keratosis is a common benign skin condition. It occurs as a gray to black raised lesion with a characteristic “stuck on” appearance. Although seborrheic keratosis appears to be very common, there are only few reports that document its transformation to in situ carcinoma.[1] Sloan and Jaworsky noted 60 cases of in situ squamous cell carcinoma occurring among 4310 cases (1.4%) of clinically diagnosed seborrheic keratosis. Malignant change seems to occur in lesions typically exposed to solar degeneration. In addition to Bowenoid transformation, invasive squamous cell carcinoma and basal cell carcinoma arising in seborrheic keratosis have also been reported.[3]

Malignant change of mostly in situ carcinoma is detected on the microscopic examination of a long-standing seborrheic keratosis located in head and neck, with a recent history of ulceration or increasing size.[2] Though occasional Bowenoid transformation of the benign growth does occur, it has not been widely recognized due to probably lack of documentation.[4] Monteagudo et al. have reported recurrence in one of the three cases of seborrheic keratosis with Bowenoid transformation.[5] Few studies have shown raised bcl-2 as an apoptotic marker in seborrheic keratosis.[6] The presence of inflammatory cells consisting of mononuclear cells, particularly lymphocytes, may be related to an involutionary process.[7] Many of these cases are probably histologically reported as in situ carcinoma or Bowen's disease. One has to be extra vigilant to observe tell-tale signs of seborrheic keratosis, at the same time not to miss the dysplastic changes of in situ carcinoma. It has to be emphasized that histopathology must be viewed in the light of clinical findings.[8] The additional findings of discoloration and ulceration extending to adjacent area helps in establishing the diagnosis.

We are presenting this case because of its rarity and clinicopathologic significance that helps in early diagnosis and its prognostic significance to the patient.