Rectal carcinoma associated with pagetoid phenomenon

ARTICLE

Primary extramammary Paget’s disease (EPD) is characterized by adenocarcinoma with apocrine differentiation that begins within the epidermis. In the secondary form of the disease, the adenocarcinoma extends into the epidermis from a contiguous organ. The latter phenomenon is known as pagetoid phenomenon and occurs in cases of rectal, cervical, and bladder carcinomas, and sebaceous carcinoma ascending infundibula to the surface epithelium. Despite the importance of diffentiation between primary and secondary EPD, the diseases can not be properly distinguished by histopathology alone. We therefore used electron microscopy to confirm the present case of rectal carcinoma with pagetoid phenomenon.

Case report

A 64-year-old Japanese woman was referred to our hospital with complaints of perianal erosion (Fig. 1) and rectal bleeding. She had noticed the lesion five years previously, and it had gradually spread. Microscopic examination of skin biopsies taken from the perianal erosion revealed the presence of Paget cells. She was admitted to the Department of Surgery of our hospital, where coexisting rectal carcinoma was found. An operation was performed to remove both lesions.

Light microscopic findings

Light microscopy revealed many Paget cells with clear cytoplasms and large pleomorphic nuclei, in addition to glandular structures (Fig. 2). Both the perianal and rectal carcinoma lesions were positively stained for PAS, CEA, and CK20, and negatively stained for GCDFP15 and CK7.

Electron microscopy

Electron microscopy revealed many microvilli protruding into the intracytoplasmic cavity in the Paget cells of the epidermis (Fig. 3). These microvilli were very similar to those observed in the rectal carcinoma cells (Fig. 4).

Discussion

Extramammary Paget's disease (EPD) derived from the epidermis or its appendages is designated as ‘primary
EPD’. Instances of secondary EPD, in which the adenocarcinoma extends into the epidermis from a contiguous organ, are relatively rare. Some visceral carcinomas, such as rectal carcinoma and anal canal carcinoma, show epidermotropism manifesting as an intraepidermal invasion, or so called pagetoid phenomenon [1]. However, it is difficult to distinguish between primary and secondary EPD based on clinical and routine histological findings. In previous studies comparing cytokeratin (CK) expression between cases of primary and secondary EPD, the combination of two markers, CK7 and CK20, was shown to be a useful index for the differentiation of primary EPD from a pagetoid spread of extracutaneous malignancies [2-5]. In a study by Watanabe et al. [2], most of the cases of secondary EPD showed the immunophenotype CK7(—)/CK20(+) (like the patient in the present study), while a small number showed CK7(+)/CK20(+).

Previous electron microscopic analyses have clearly indicated the many similarities between adenocarcinoma cells and Paget cells; e.g.both cell types have microvilli projecting into the intracytoplasmic cavity [5].

CONCLUSION

We concluded that electron microscopy was a very useful techniques for differentiating between EPD and pagetoid phenomenon.

REFERENCES

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