Scrotal calcinosis: pathogenetic link with epidermal cyst

Abstract

Scrotal calcinosis is a rare entity characterised by multiple calcified nodules in the scrotal skin. Various pathogenetic mechanisms have been postulated in the literature to explain the origin of these nodules; however, debate continues among variable opinions and evidence. We report two cases of scrotal calcinosis developing from an epidermoid cyst with demonstration of pathology at various stages, thereby suggesting calcification of epidermal cysts as an initiating event in the pathogenesis of the disease, at least in a few cases.

Background

Scrotal calcinosis (SC) is a rare disease of the scrotum characterised by multiple calcified and asymptomatic nodules in the scrotal skin. Although the first description of SC by Lewinski dates back to 1883, its aetiology and pathogenesis still remain a matter of controversy. According to few authors, SC is secondary to dystrophic calcification of epidermal cysts, eccrine epithelial cysts or degenerated dartos muscle, while others consider it as idiopathic SC due to failure to detect any associated abnormality.¹ Therefore, a vigilant approach in histopathological examination is essential to explore the underlying pathogenetic mechanism.

Case presentation

Case 1

A 28-year-old man presented with painless swelling of the scrotum for 6 months, gradually increasing in size. There was no history of sexually transmitted disease or trauma. No other specific symptoms were present.

On physical examination he was of average build with unremarkable general examination. Examination of the scrotum revealed a cystic swelling measuring 1.5 cm over the ventral surface. In addition, multiple, hard, nodular lesions were present adjacent to the cystic swelling, the largest measuring 1.2×9 mm. There were no areas of ulceration. According to the patient, these were long-standing lesions which were ignored. His primary concern was the most recent lesion. Biochemical examination demonstrated serum calcium, phosphate and albumin to be within the reference range.

Excision of the cyst along with adjacent lesions was performed and sent for histopathological analysis. Gross examination of the excised specimen showed multiple whitish hard nodular lesions along with a cystic lesion containing keratinous material measuring 1.5 cm (figure 1A) and (figure 1B case: 2). Microscopic examination revealed a single cystic structure lined by a stratified squamous epithelium with abrupt keratinisation (figure 2A). The surrounding dermis showed another small cyst with an attenuated epithelium (figure 2B) and minute calcific deposits in one aspect of the wall and the formation of large deposits focally (figure 2C). The rest of the nodules were entirely composed of calcified material devoid of any epithelial lining.

Figure 1.

(A) Gross photograph of the scrotum showing a large single cystic structure surrounded by multiple calcified nodules of varying size. (B) Gross photograph of another case showing small whitish calcified nodules over the external surface of the scrotum.

Figure 2.

Sequential microphotographs demonstrating evolution of the disease. (A) Precursor cystic structure lined by a stratified squamous epithelium, (B) Another cyst with an attenuated epithelium and minute calcific deposits in the wall, (C) Large calcific deposits at one aspect of the cyst and (D) Calcified nodules devoid of any lining epithelium representing the terminal stage of the disease.

Case 2

A 35-year-old man presented with multiple hard nodular swellings of the scrotum for the past few years which were increasing in number. There were no other symptoms. Examination of the scrotum revealed multiple hard nodules with intact overlying skin. Biochemical examination demonstrated serum calcium, phosphate and albumin to be within the reference range. Excision of the small part of the scrotum was performed and gross examination of the excised specimen showed multiple whitish hard nodular lesions, the largest measuring 6 mm in diameter. Microscopic examination revealed predominantly multiple calcified nodules corresponding to gross appearance (figure 2D). In addition, a small single cystic structure was identified with stratified squamous epithelium lining conforming to the morphology of epidermoid cyst.

Treatment

Both patients were managed by surgical excision.

Outcome and follow-up

Both patients are doing well at 6-months follow-up.

Discussion

SC is a rare disease of the scrotal skin which usually presents with multiple asymptomatic, calcified nodules; lesions are usually ignored initially and patients commonly seek the clinician's opinion years or decades after the initial onset.² Only a few hundred cases have been reported worldwide to date.³ Exact incidence is difficult to report as this entity is usually described in the form of individual case reports and limited numbers of case series are available in the literature.^3–7 Though the most common presentation is between the third and fourth decades of life, both adult and paediatric age groups may be affected with the age range being 9–85 years.⁸ Despite extensive calcinosis of the scrotum, systemic calcium-phosphorus metabolism is unaltered; therefore, substantial contribution of localised pathogenic mechanisms cannot be ignored and should be the target of research.

Detailed histopathological examination of the surgical specimen is essential to unveil the underlying pathogenesis. On the basis of the accompanying morphological findings, various hypotheses have been postulated that connect the pathology to dystrophic calcification of pre-existing structures including epidermal cyst, eccrine epithelial cyst and degenerated dartos muscle.¹ However, inability to find any clues in a few cases compounds the problem and promotes the use of ‘idiopathic’ terminology in such cases.

In the index cases, the calcinosis is secondary to dystrophic calcification of epidermoid cysts, as evident with histopathology. Since the lesions in these cases displayed a spectrum of morphological changes, we were further able to elucidate the possible pathogenetic mechanism. The earliest lesion was the epidermoid cyst without any evidence of calcification. One of the cysts demonstrated the stage of evolution through specks of calcification in the wall up to focal nodular deposits. The rest of the calcified nodules were devoid of any lining epithelium, probably representing the end stage of the disease. Histopathological examination at this stage and the inability to demonstrate any fresh precursor lesions probably contribute to ‘idiopathic’ terminology in a few case series.

Although there is no consensus, dystrophic calcification of epidermal cysts is a favoured theory to explain pathogenesis of the disorder in the literature. Similar to our observations, Shah and Shet also tried to explain the pathogenesis based on a spectrum of morphological changes. According to them, precursor lesions are cystically dilated epidermal cysts with a variable amount of keratin in the centre. With time, these cysts develop specks of calcification and finally evolve into nodules of calcification with attenuation or disappearance of the lining epithelium. Even in an advanced stage, epithelial remnants can be highlighted via cytokeratin immunostaining.⁷

Whatever the underlying pathogenesis of this condition, the only recommended therapeutic modality is surgical excision. Patients usually require surgical intervention either for cosmetic concern or due to intense pruritus or ulceration in the nodules. Smaller lesions are usually amenable to the novel pinch punch excision, but larger lesions may require a wide excision. Extensive disease involving the whole scrotum or florid recurrent disease will require complex scrotal reconstruction.⁹

Even though the risk of recurrence after excision is also controversial, the patient should be informed about the possibility of recurrence. Recurrence may be due to left-over microscopic foci of calcification. A perfect surgical approach with excision of even the smallest lesion is crucial to prevent recurrence in the future.

Learning points.

▸ Amid discussions regarding the aetiology and pathogenesis of scrotal calcinosis, this report of two cases describes the development of scrotal calcinosis from the dystrophic calcification of epidermoid cysts. A few points should be kept in mind while dealing with such cases:

• A detailed histopathological examination of the surgical specimen is essential to demonstrate the precursor lesion and progression of the lesion into end-stage calcification.

• Even in the so-called ‘idiopathic’ cases, a vigilant search for epithelial remnants and cytokeratin immunostaining might be beneficial to elucidate the underlying pathogenesis.

• To prevent recurrence, a perfect surgical approach with excision of even the smallest lesion is warranted.