Case Presentation: A 49-year old man presented to the emergency department (ED) with dizziness and lethargy. He had a history of hypertension, anemia, and pilomatrix carcinoma (PC), a rare cutaneous malignancy. This was diagnosed one year prior and treated with wide excision with negative margins. He was lost to follow up for 7 months prior to presentation. He reported decreased energy, unintentional weight loss, and new painless lumps in several areas of his scalp and skin. He also endorsed muscle spasms, headache, dry cough, and generalized weakness.On admission, vital signs were normal and physical exam showed significant bilateral inguinal lymphadenopathy and diffuse nodular indurated lesions. Basic labs showed a stable anemia, and otherwise were within normal limits. CT imaging revealed pulmonary nodules, extensive mediastinal adenopathy, hepatic and splenic lesions, multiple paraspinal and subcutaneous lesions, and a thyroid mass, all thought to be due to metastatic disease. MRI brain revealed multifocal cortical and subcortical metastatic lesions and nodular lesions overlying the scalp. Given the rarity of metastasis of PC, a biopsy of the patient’s left inguinal lymph node was performed to confirm the diagnosis of stage IV PC.Pending further workup, the patient received whole brain radiation therapy and dexamethasone. The patient’s biopsy specimen was further analyzed using next generation sequencing (NGS). Literature has shown a strong association between PC and wnt/b-catenin pathway activation.1 Unexpectedly, this patient’s NGS testing revealed no mutations in this pathway and instead showed evidence of integrated HPV18. With these results and in the absence of guidelines for metastatic PC, evidence for squamous cell carcinoma of the head and neck was used to guide treatment. Chemotherapy with carboplatin, paclitaxel, and pembrolizumab was initiated. MRCP one month later demonstrated disease progression with new hepatic metastases. Chemotherapy was converted to oxaliplatin, pemetrexed, and pembrolizumab, without response. The patient ultimately transitioned to supportive care and died 4 months after his diagnosis of metastatic disease.
Discussion: PC is a rare cutaneous malignancy stemming from follicular matrix cells with approximately 140 cases reported worldwide.2 Clinical presentation is typically a single nontender, firm, violaceous dermal lesion, most commonly in the head or neck. PC is most prevalent among men in the sixth and seventh decades of life.1 It tends to be locally aggressive with a high likelihood of recurrence despite excision. After wide excision, 18 to 23 percent of lesions recurred locally. While less common, metastatic disease is reported in 10 to 16 percent of cases, most frequently in the lungs and lymphatics.3Given the rarity of this malignancy, there are no consensus guidelines on treatment. For local disease, Mohs micrographic surgery is currently thought to offer the best prognosis for local PC given the improved margin control achieved with this technique. For metastatic disease, chemotherapy and radiation have been reported ineffective.3
Conclusions: PC is a rare and aggressive cutaneous malignancy with poor treatment options for metastatic disease. PC often initially presents as a single nontender, firm, violaceous dermal lesion, most commonly in the head or neck. Recurrence is common, so patients with prior resected PC presenting with new lesions or symptoms should be evaluated for local or distant recurrence.