AT BALL DERMPATH, we are fascinated by interesting and difficult cases, and we love to share them with our colleagues. Here is a sampling of some of our prior cases-of-the-month as they appeared in our monthly email newsletter.
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#1. Clinical impression: R/O atypical sebaceous adenoma. From the lateral back of an 82-year-old man with no history of melanona.
H&E 10x
Diagnosis: Pathology shows a well circumscribed lesion consisting of numerous basaloid cells and scattered larger multi-vacuolated cells. This is an example of a sebaceous epithelioma. Sebaceous epithelioma is a benign sebaceous neoplasm that differs from sebaceous adenoma in the proportion of basaloid cells it contains. While sebaceous epithelioma has a larger percentage of immature basaloid cells, the sebaceous adenoma will have larger component of differentiated mature sebocytes.
Discussion: The findings of sebaceous adenoma, epithelioma, and/or carcinoma (but not sebaceous hyperplasia) should prompt consideration of Muir Torre syndrome. Muir Torre syndrome is a hereditary cancer syndrome in which patients are prone to sebaceous neoplasms and internal malignancies, most commonly gastrointestinal and genitourinary carcinomas. Neoplasia results from defects in DNA mismatch repair proteins (most commonly MSH2, but also MSH6 and MLH1, among others), which manifest as microsatellite instability. Initial evaluation requires a detailed family and personal history that includes types of carcinomas and ages of onset.
Additional diagnostic studies may include immunohistochemical evaluation of mismatch repair protein expression (see inset upper right), testing for microsatellite instability, and/or germline mutation analysis of mismatch repair protein sequence. Immunohistochemical evaluation of mismatch repair proteins may provide helpful information in the workup but should not be relied upon in isolation to rule in or rule out the disease. Rather, results must be interpreted in the correct clinical context and generally additional studies are still needed for a more definitive diagnosis.
MLH1 10x
H&E 40x
#2. Clinical impression: R/O pyogenic granuloma. From the umbilical region of a 44-year-old male.
H&E 2x
Diagnosis: Umbilical pilonidal sinus/cyst
Discussion: Pilonidal sinus/cyst most commonly occurs in the sacrococcygeal area, but less commonly can occur in unusual areas such as on the ear, scalp, chest, genital region, and umbilicus. The etiology is believed to be from ingrown hairs; sacrococcygeal pilonidal sinus was once known as “Jeep Seat” as it was common during WWII (80,000 soldiers were affected between 1941-1945), and was thought to be due to prolonged rides in bumpy Jeeps causing pressure and irritation. Like its sacrococcygeal counterpart, umbilical pilonidal sinus is more common in young men, and predisposing factors include a deep umbilicus, hirsuitism, and obesity. On path we see the wall of the sinus lined by stratified squamous epithelium and/or granulation tissue, a dermis that is intensely inflamed, and free hair shafts with a foreign body giant cell reaction. Definitive treatment is controversial. Approaches vary from conservative (removal of hair, cleaning, drainage, follow up) to sinus tract excision to umbilectomy.
H&E 2x
H&E 10x
H&E 20x
#3. Clinical impression: ISK vs carcinoma. From the trunk of a 75-year-old male.
H&E 4x
Discussion: From low power the extensive acantholysis of this lesion brings to mind a differential diagnosis that includes Grover’s disease as well as the other acantholytic dermatoses such as Darier disease and Hailey-Hailey disease or pemphigus vulgaris. Although, if you look carefully at the images below you will notice marked keratinocyte atypia.
Acantholytic SCC is a variant with a marked male predominance. It is generally believed to have a slightly more aggressive course than traditional SCC. However, there are few large scale, well controlled comprehensive studies on this topic.
H&E 20x
H&E 20x
H&E 40x
#4. Clinical impression: SCC vs trauma. From the 2nd web space right hand of an 89-year-old male.
PAS Stain 40x
Discussion: This is an example of cutaneous Phaeohyphomycosis. Phaeohyphomycosis is a term used for a wide variety of different dematiaceous (pigmented) fungal infections, including superficial, subcutaneous and visceral forms of disease. While a myriad of different fungal species may be implicated, among the most common are Exophiala, Alternaria, Wangiella, Curvularia, Fonsecaea, Cladosporium, and Phialophora ssp.
Cutaneous infection commonly follows traumatic implantation, as in this case. A common histopathological finding is a subcutaneous cyst (figures 2 and 3) or abscess containing inflammation, necrotic debris, foreign body and fungus. Dematiaceous fungi are ubiquitous in nature, and traumatic implantation is a common occurrence. Here we can see the culprit: a foreign body with rigid cells walls, which we recognize as plant material – also known as a splinter. On higher power and with the use of a PAS stain, we can identify fungal hyphae around the edge of the splinter (figure 4). Notice the striking appearance under polarized light microscopy (figure 5)!
H&E 20x
PAS stain 20x
#5. Clinical impression: R/O verruca. From the plantar foot of a 52-year-old female.
Sections show a slightly polypoid lesion. The epidermis is uninvolved, while the dermis contains a spindle cell proliferation. On high power we can see that cells are bland with wavy nuclei in an eosinophilic background. The lesion is slightly vascular and occasional mast cells are seen.
Immunohistochemical staining shows that the lesion is strongly and diffusely positive for CD34. The remainder of the immunohistochemical panel is negative, including Factor XIIIA, EMA, SMA, S-100, MITF and SOX10. Our differential included: superficial acral fibromyxoma, cellular digital fibroma, medallion-like dermal dendrocyte hamartoma, and dermatofibrosarcoma protuberans (DFSP).
The lesion was excised. Within the excision, CD34 shows a small amount of residual lesion. Deep dermal and subcutaneous tissues are uninvolved. (See figures above.)
Discussion of differential:
Superficial acral fibrmyxoma: first described in 2001, and classically located around the nail apparatus (although there are exceptions, including the palm of the hand), this lesion consists of CD34+ spindled cells set within a variably myxoid stroma. This case lacks myxoid stroma and is on the sole of the foot.
Cellular digital fibroma: first described in 2005 and thought by some to be on a spectrum with superficial acral fibromyxoma, these bland CD34+ acral spindle cell lesions may mimic DFSP on histopathology.
Medallion-like dermal dendrocyte hamartoma (also known as plaque-like CD34 positive dermal fibroma): first described in 2004, this bland spindle cell proliferation was traditionally described as a plaque on the trunk showing positivity for both Factor XIIIA and CD34; however exceptions to this paradigm are increasingly being reported, including a polypoid variant and Factor XIIIA negativity.
DFSP: a low grade malignancy characterized by CD34+ spindled cell sarranged in a storiform pattern; deep extension of the lesion with trapping of subcutaneous fat is an important diagnostic features.
Conclusion: In consideration of the above, this case remains difficult to classify definitively. However, the excisional specimen confirms that this lesion is superficial in nature, thereby ruling out the possibility of DFSP. We favor a diagnosis of medallion-like dermal dendrocyte hamartoma.