Pyogenic granuloma-like Kaposi sarcoma presenting in an HIV-negative man who has sex with men

Abstract

A 36-year-old immunocompetent man who have sex with men first presented to the plastics team with an ulcerating lesion on his left first toe. The lesion was suggestive of pyogenic granuloma (PG) clinically and histologically. Two years later, the same patient presented to the dermatology clinic with a new erythematous lesion with intermittent bleeding on the left second toe. Clinically, this lesion was suggestive of another PG. However, the histology of the skin curettage revealed part of a PG merging with an atypical spindle cell proliferation with characteristic ‘sieve-like’ appearance in keeping with Kaposi sarcoma. This was confirmed with human herpesvirus-8 immunohistochemistry staining. PG-like Kaposi sarcoma is an uncommon variant of Kaposi sarcoma. Often not considered clinically or histologically, a deep skin biopsy is essential to establish the right diagnosis. Our case highlights the need to consider Kaposi sarcoma as a differential diagnosis in all patients, including HIV-negative individuals, presenting with PG-like lesions.

Background

Pyogenic granulomas (PGs) are a common in general practice and dermatology clinics. It is thought that up to 0.5% of childhood skin nodules are PGs and that they occur in up to 5% of pregnancies.^{1 2} Although their exact aetiology is unknown, PGs are most often linked to a traumatic insult to skin or mucosa, however, other causes like hormonal, infectious or pharmaceutical are known.³

Contrastingly, PG-like Kaposi sarcoma (PG-like KS) is uncommon and rarely considered clinically. Due to this, it may be missed in a non-representative superficial biopsy. In addition, this clinicopathological variant of Kaposi sarcoma (KS) can present in HIV-negative individuals. Our case highlights the need to consider KS as a differential diagnosis in all patients presenting with PG-like lesions.

Case presentation

A 36-year-old immunocompetent HIV-negative man who have sex with men first presented to the plastics team with a new ulcerating lesion on his left first toe. Clinically, the lesion was suggestive of PG. An excisional biopsy confirmed the histological findings of a PG.

Two years later, the same patient presented to the dermatology clinic with a new erythematous lesion with intermittent bleeding on the left second toe. Clinically, this lesion was similar and also suggestive of another PG (figures 1 and 2). Curettage and cautery were arranged to remove this second lesion.

Figure 1.

A 36-year-old HIV-negative man presenting with an erythematous lesion with intermittent bleeding on the left second toe, suggestive of a pyogenic granuloma.

Figure 2.

Dermoscopy showed a red homogenous area with white collarette and vascular structures, all features suggestive of a pyogenic granuloma.

Investigations

The histology of the second lesion (figure 3) demonstrated an ulcerated polypoid skin lesion with partial PG-like morphology in the dermis. However, this merged with features strongly suggestive of KS, with confluent area of proliferating atypical spindle cells demonstrating a ‘sieve-like’ appearance due to extravasated red cells (figures 4 and 5). There was mitotic activity and Periodic acid-Schiff (PAS) stain highlighted characteristic eosinophilic globules within this area. Immunohistochemistry for CD31, CD34 and D2-40 was positive and human herpesvirus-8 (HHV-8) showed diffuse nuclear positivity (figure 6).

Figure 3.

The histology of the curettage scrapings demonstrated an ulcerated polypoid skin lesion with vaguely lobulated proliferating vessels in the dermis.

Figure 4.

The low power image suggests top half of the histology is consistent with pyogenic granuloma which is the same as a lobulated capillary haemangioma.

Figure 5.

In the base, there is a characteristic monomorphous spindle cell proliferation with a ‘sieve-like’ appearance with extravasated red cells and mitotic activity.

Figure 6.

Immunohistochemistry for human herpesvirus-8 showed diffuse nuclear positivity, suggesting the initial presenting lesion was not of a pyogenic granuloma, but rather a Kaposi sarcoma in an HIV-negative gay man.

When the slides of the initial lesion on the left first toe was reviewed, there were a few cells that stained positive for HHV-8. A subsequent HIV screening test was negative.

Differential diagnosis

The main differential diagnosis for this presentation was that of a PG. On examination, the first lesion on the hallux was suggesting of a PG as it was an ulcerating lump with intermittent bleeding as shown in figures 1 and 2. The first excisional biopsy initially suggested these findings due to the appearance of vaguely lobulated and proliferating vessels in the dermis. However, as mentioned above, the curettage biopsy of the second lesion suggested a different diagnosis. On retrospective, re-evaluation of his initial excisional biopsy the conclusive diagnosis was confirmed in the first lesion as well.

Treatment

The patient only required an excisional biopsy of his first lesion. For his second lesion, he initially underwent curettage and cautery which confirmed the underlying diagnosis. However, this second lesion reoccurred 6 months later. At his second presentation, he underwent an excisional biopsy of this lesion. The patient did not require any other treatment.

Outcome and follow-up

The results from the second curettage biopsy gave conclusive results. The confluent areas of atypical spindle cell proliferation with ‘sieve-like’ appearance and extravasated red cells and mitotic activity suggested a diagnosis other than a PG. Also, there was positive immunohistochemistry to CD31, CD34, D2-40 and HHV-8. Therefore, this confirmed that the diagnosis was not a PG, but rather, a pyogenic granuloma-like KS.

Currently, almost 4 years after his first lesion and 2 years after his second lesion, the patient has not had any further recurrences. This patient remains under routine follow-up to monitor for new lesions.

Discussion

PG is a reactive proliferation of capillary blood vessels commonly presenting as red raspberry-like lesion.¹ PG can be frequently found in the head and neck regions, upper trunk and extremities. The pathophysiology is unknown, but it is often associated with trauma, infection, immunomodulatory medications and pregnancy. However, in some cases, an underlying trigger is not identified.

KS is a multicentric vascular hyperplasia and is one of the three proliferative diseases associated with HHV-8.⁴ The development of KS is commoner in older men of Mediterranean or African descent, immunosuppressed individuals and those with HIV. HHV-8 has been implicated in the pathophysiology of all variants of KS.²

First reported in the literature in 1959, PG-like KS is considered a clinicopathological variant of KS.⁵ This entity is rare, but has been reported in both HIV-positive and HIV-negative individuals.^{6 7} Interestingly, it appears to present more commonly in male individuals and the most common reported location is the plantar aspect of feet.⁶

Histologically, this form of KS can mimic a PG in superficial biopsies. Both lesions stain positive for CD31, CD34, smooth muscle actin and factor VIII-related antigen.⁸ In addition, D2-40 immunostaining, usually an indicator of KS, can be negative.⁹ HHV8 latent nuclear antigen-1 is a specific immunoperoxidase marker² that helps differentiate PGs and PG-like KS.

It remains crucial to distinguish between PGs from PG-like KSs due to need to follow-up patients with KS every 6–12 months¹⁰ to examine for recurrence or new lesions. Furthermore, the identification of KS will trigger the need to do further blood tests, including HIV screening, to ensure immunocompetence. Our case highlights the importance of considering KS in the differential diagnosis of PG-like lesions.

Learning points.

• Pyogenic granuloma-like Kaposi sarcoma (PG-like KS) is an uncommon clinicopathological variant of Kaposi sarcoma (KS).

• Early clinical KS lesions can appear to be PGs.

• PG-like KS can present in HIV-negative individuals.

• KS needs to be considered as a differential diagnosis in all patients presenting with pyogenic granuloma-like lesions.

• Excisional biopsies or deeper shaves may offer better long-term outcomes for patients with PG-like KS