Drug-induced GD most likely is caused by vascular insults that lead to deposition of immune complexes in vessels causing inflammation and a consequent granulomatous infiltrate.21,22 Although cordlike lesions in the subcutaneous tissue on the trunk commonly are reported, the presentation of GD can vary considerably. Other presentations include areas of violaceous or erythematous patches or plaques on the limbs, intertriginous areas, and upper trunk. Diffuse macular erythema or small flesh-colored papules also can be observed.23
Granulomatous dermatitis secondary to drug reactions can have varying morphologies. The infiltrate often can have an interstitial appearance with the presence of lymphocytes, plasma cells, histiocytes, eosinophils, and multinucleated giant cells.24 These findings can be confused with interstitial granuloma annulare. Other cases, such as in our patient, can have discrete granulomata formation with a sarcoidlike appearance. These naked granulomas lack surrounding inflammation and suggest a differential diagnosis of sarcoidosis and infection. Use of immune checkpoint inhibitors (CIs) and kinase inhibitors has been proven to cause sarcoidosislike reactions.25 The development of granulomatous/sarcoidlike lesions associated with the use of BRAF and MEK inhibitors may clinically and radiographically mimic disease recurrence. An awareness of this type of reaction by clinicians and pathologists is important to ensure appropriate management in patients who develop GD.26
Checkpoint inhibitor–induced GD that remains asymptomatic does not necessarily warrant treatment; however, corticosteroid use and elimination of CI therapies have resolved GD in prior cases. Responsiveness of the cancer to CI therapy and severity of GD symptoms should be considered before discontinuation of a CI trial.25
One case report described complete resolution of a GD eruption without interruption of the scheduled BRAF and MEK inhibitor therapies for the treatment of metastatic melanoma. There was no reported use of a steroidal cream or other topical medication to aid in controlling the eruption.27 The exact mechanism of how GD resolves while continuing therapy is unknown; however, it has been suggested that a GD eruption may be the consequence of a BRAF and MEK inhibitor–mediated immune response against a subclinical area of metastatic melanoma.28 If the immune response successfully eliminates the subclinical tumor, one could postulate that the inflammatory response and granulomatous eruption would resolve. Future studies are necessary to further elucidate the exact mechanisms involved.
There have been several case reports of GD with vemurafenib treatment,29,30 1 report of GD and erythema induratum with vemurafenib and cobimetinib treatment,31 2 reports of GD with dabrafenib treatment,27,30 and a few reports of GD with the BRAF inhibitor dabrafenib combined with the MEK inhibitor trametinib,28,32,33 all for the treatment of metastatic melanoma. Additionally, a report described a 3-year-old boy who developed GD secondary to vemurafenib for the treatment of Langerhans cell histiocytosis.34 We present a unique case of BRAF and MEK inhibitor therapy–induced GD in the treatment of metastatic cholangiocarcinoma with vemurafenib and cobimetinib.
BRAF and MEK inhibitor therapy is used in patients with metastatic melanomas with a positive BRAF V600E mutation. Due to advancements in next-generation DNA sequencing, these therapies also are being tested in clinical trials for use in the treatment of other cancers with the same checkpoint mutation, such as metastatic cholangiocarcinoma. Cutaneous reactions frequently are documented side effects that occur during treatment with BRAF and MEK inhibitors; GD is an uncommon finding. As the utilization of BRAF and MEK inhibitors increases for the treatment of a variety of other cancers, it is essential that clinicians and pathologists recognize GD as a potential cutaneous manifestation.